Process for the production of metal electrodeposits



PROCESS FOR THE PRODUCTION OF METAL ELECTRODEPOSITS Wenneinar Strauss, Dusseldorf Benrath, Alfred Kirstahler, Dusseldorf, and WoIf Dieter'WiIImund, Dusseldm'f-Holthausen, Germany, assignors to Dehydag, Deutsche Hydrierwerke G. In. b. H., Dusseldorf, Germany, a corporation of: Germany No Drawing. Application September 28, 1954 SerialNo. 458,985

Claims priority, application Germany April 22, 1954 11 Claims. (Cl. 204 -52) This invention relates to a process for producingbright metal electrodeposits, andmore particularly to electroplating solutions containing additives. which eliminate the adverse effects of impurities in such solutions upon the electrodeposits producedtherefrom. 7

It is Well known in the electroplating, art that the brightening effect of brightening agents added to electroplating solutions is seriously impaired by certain impurities contained in such solutions. have such an impairing elfect. upon electrodeposits include those substances which cause the hardnessof water as well as impurities which occur intechnical grade metal salts employed to prepare electroplating baths, particularly copper-plating baths. 7

The obvious. solution to this problem is to employ distilled water and chemically pure metal salts for the preparation of electroplating. baths intended to be used in conjunction with brightening agents. However, it is evident that the use of such chemically pure components;

would not only be very impractical but also render the cost of electroplating objects sohigh as to make bright plated. articles too costly.

It is, therefore, an object ofthe present invention to provide a method. of electroplating objects in electroplating baths containing brighteningagents whichmakes it possible to produce bright electrodeposits despite. the presence of interfering impurities in the electroplating bath.

Another object of this invention is to. provide additives for electroplating baths containing brightening agents which will render impurities present in the bath impotent as interfering substances in the production ofzbrighb electrodeposits.

Other objects and advantages. will become apparent as,

the description of. our invention. proceeds;

We have found that the interfering elfectof impurities in electroplating baths containing; brightening. agents-can be eliminated by adding to such electroplating baths tertiary amino compounds, free from. carboxyl. groups, having the general structural formula wherein G is'selected from the group consistingofhal'ogen, cyano, thiocyano and nitro, R is selected from'the group consisting of lower alkylene, monohydroxy lower alkylene and. phenyl, and. R and R are selectedfrom the group consisting ofv lower alkyl, monohydroxy lower alkyl, phenyl, cyclohexyl and. heterocyclicradicals which include the nitrogen atom selected from the group consisting of morpholino and piperidino, the radical? G and the nitrogen atom being attached to carbon atoms of radical R.

Examples of compounds which are suitable for modify- Impurities which.

. United StatesPatent O 2,842,488 Patented July 8, 1958 ice ing electroplating baths containing brightening agents in accordance with our invention are the following:

i-dioxyethylamino-3-chloropropano1-2 N (3-chloro-2-oxypropy1-N methyl-aniline Garcia-01103011101 H] 1 N-(3-chloro-2-nxypropyl)'-N-methyl cycloliexylamlnw N,N-dicyc1ohexy1-N-2?chloro-ethylamlne.

N-2-chloroethy1-piperidine N -2-ch1oroethyl-morphol1ne V C H;

p o n, 'N-,N-dimethyl-4-bromoaniline C H3 N,N-dimethyl-4-ehloroaniltne N/C 2H6 CzHl l N,N- diethyl'-2-chloroaniline' N,N-dimethy1-3nitroanillne Bis- (2-bromoethy1) -benzylamine I CHaCHaBt B-Diethylamino-propionitrile and the like.

Tertiary amino compounds of this type may also be employed in the form of their salts of inorganic and organic acids, or in the form of the corresponding quaternary ammonium compounds.

In order to obtain the desired result the additives in accordance with our invention are added to electroplating baths, modified with brightening agents, in amounts ranging from 0.01 gm./liter and 20 gm./liter of bath, preferably from 2 to 8 gm./1iter of bath. The particular amount required varies from one specific compound to the other and also depends upon the nature of the brightening agents employed as well as upon the type and amount of impurities present. In general, objects are electroplated in a bath modified in accordance with our invention at a temperature ranging between 30 and C. .with .a current density between 0.5 and 15 r Electroplating baths containing brightening agents and modified in the above manner in accordance with our invention will produce bright and lustrous electrodeposits over the entire effective range of current densities despite the presence of impurities of the above-described nature in the bath. Moreover, the additives in accordance with our invention have the further advantage that they increase the ductility of the electrodeposit produced from electroplating baths modified with such additives.

The additives of our invention are efiective in all those electroplating baths which contain magnesium and calcium ions due to the use of hard tap water, and ferric ions introduced by the use of technically pure metal salts in the preparation of the electroplating solution. How ever, it has beenfound that they do not act as watersoftening agents in the usual sense, and that they cannot be replaced by the typical water-softening agents such as sequestering agents or detergents. Nevertheless,

these additives are capable of completely eliminating the adverse effect of the above-described impurities upon the brightness of electrodeposits produced from baths containing such impurities and brightening agents.

Although the exact theoretical reason for their action is not fully understood, it .is believed that their eifect' comes into play at the surface of the metal object, which is indicated by the high concentrations in which these substances must be used in some instances to produce the desired effect.

The use of the additives in accordance with our invention does not require any changes in the conditions under which objects are usually electroplated in metal salt baths, particularly with respect to temperature and current densities. As amines, they are soluble in acid metal salt solutions, particularly in electroplating baths made from copper, salts, and they are not decomposed by the action of heat or electric current during the plating process.

The additives of our invention can be employed to modify all types of electroplating baths containing brightening agents and in which the qualities of electrodeposits produced therefrom are adversely aifected by the presence of impurities of the type described above. Thus, the

additives may be used in electroplating baths for elec-w trodepositing zinc, nickel, chromium, precious metals,

. hydrin.

Example 1 A copper-plating bath was prepared which contained distilled water, 200 gm./1iter crystalline chemically pure copper sulfate and 60 gm./liter chemically pure sulfuric acid. The bath was then modified with 0.75 gm./liter N,N-dipropyldithiocarbamic acid-n-butylester-w-sodium sulfonate as a brightening agent. Iron objects were then electroplated in the modified bath using a current density range of 0.5-8 amp./dm. The copper deposits produced thereby were bright and lustrous.

As a comparison, a copper-plating bath having the same composition was prepared by using hard tap water instead of the distilled water, and technical grade copper sulfate rather than chemically pure copper sulfate. This bath was then modified with a brightening agent as above. Iron objects copper-plated in such a bath were provided with a copper deposit which was not as bright and lustrous as when distilled water and chemically pure copper sulfate were used to make up the copper-plating solution.

Example 11 A copper-plating bath was prepared from hard tap water, 200 gm./liter technical grade copper sulfate and 60 gm./liter sulfuric acid. This bath was then modified by adding 0.75 gm./liter N,N-dipropyl-dithiocarbamic acid-n-butylester-w-sodium sulfonate. Thereafter, 2.5 gm./liter Z-diethylamino-ethylchloride-l were added. Iron objects were the electroplated in this bath within a current density range of 0.5-8 amp./dm. The copper deposits produced thereby were bright and lustrous, as well as being highly ductile.

Example III To a copper electroplating bath, prepared as described in Example II, where added 0.5 gm./liter N,N-diethyldithiocarbamic n propylester w soditun sulfonate as brightening agent together with 4 gm./liter N-2-chloroethyl-piperidine. Iron objects were then electroplated in this bath within a current density range of 0.5-8 amp./dm. The copper deposits produced thereby were bright and lustrous, as well as being highly ductile.

Example IV To a copper electroplating bath, prepared as described in Example II, were added 0.5 gm./1iter N,N-diethyldithiocarbamic n propylester w sodium sulfonate and thereafter 2 gm./liter of the quaternary compound, prepared by mixing together morpholine with epichloro- Iron objects were then electroplated in this bath within a current density range of 0.5-8 amp./dm. The copper deposits produced thereby were bright and lustrous, as well as being highly ductile.

Example V were-then electroplated in this bath within a current density range of 0.5-8 amp./drn. The copper deposits produced thereby were bright and lustrous, as well as being highly ductile.

While we have illustrated certain specific embodiments of our invention, we wish it to be understood that various changes and alterations can be made without departing J from the spirit of our invention or the scope of the appended claims.

We claim:

1. In a process of producing bright copper electrodeposits from acid copper electroplating baths comprising hard water, technical grade copper salts and a sulfonic acid brightening agent, steps which comprise adding to said acidic copper electroplating baths from 0.01 to 20 gm./ liter of an N-substituted monoamino compound, free from carbOXyl groups, selected from the group consisting of compounds having the structural formula wherein R is selected from the group consisting of lower alkylene, monohydroxy lower alkylene and phenyl, G is a halogen atom, and R and R are selected from the group consisting of lower alkyl, monohydroxy lower alkyl, phenyl, cyclohexyl and heterocyclic radicals which include the nitrogen atom selected from the group consisting of morpholino and piperidino, the radical G and the nitrogen atom being attached to carbon atoms of radical R, their salts and their quaternary ammonium compounds formed with epichlorohydrin, and electrodepositing copper from said baths, whereby the impurities contained in said water and said technical grade copper salts are prevented from interfering with the brightening action of the brightening agent.

2. In the process of producing bright copper electrodeposits from acidic copper electroplating baths comprising hard water, technical grade copper salts and a sulfonic acid brightening agent, the steps which comprise adding to said acidic copper electroplating baths from 0.01 to 20 gm./liter of a quaternary ammonium compound formed 'by reacting epichlorohydrin with an N-substituted monoamino compound, free from carboxyl groups, having the structural formula wherein R is selected from the group consisting of lower alkylene, monohydroxy lower alkylene and phenyl, G is a halogen atom, and R and R are selected from the group consisting of lower alkyl, monohydroxy lower alkyl, phenyl, cyclohexyl and heterocyclic radicals which include the nitrogen atom selected from the group consisting of morpholino and piperidino, the radical G and the nitrogen atom being attached to carbon atoms of radical R, and electrodepositing copper from said baths, whereby the impurities contained in said water and said technical grade copper salts are prevented from interfering with the brightening action of the brightening agent.

3. In a process of producing bright copper electrodeposits from acidic copper electroplating baths comprising hard water, technical grade copper salts and a sulfonic acid brightening agent, the steps which comprise adding to said acidic copper electroplating baths from 0.01 to 20 gm./liter of a compound, free from carboxyl groups having the structural formula wherein R is selected from the group consisting of lower alkylene, mono hydroxy lower alkylene and phenyl, G is selected from the group consisting of halogen, cyano, thiocyano and nitro, and R and R are selected from the group consisting of lower alkyl, monohydroxy lower alkyl, phenyl, cyclohexyl and heterocyclic radicals which include the nitrogen atom selected from the group consisting of morpholino and piperidino, the radical G and the from interfering with the brightening action of the sulfonic acid brightening agent;

4. In a process of producing bright copper electrodeposits from acidic copper electroplating baths comprising hard water, technical grade copper salts and a sulfonic acid brightening agent, the steps which comprise adding to said acidic copper electroplating baths from 0.01 to 20 gm./liter of Z-diethylamino-ethylchloride-1, and electrodepositing copper from said baths, whereby the impurities contained in said hard water and said technical grade copper salts are prevented from interfering with the brightening action of the sulfonic acid brightening agent.

5. In a process of producing bright copper electrodeposits from acidic copper electroplating baths comprising hard water, technical grade copper salts and N,N- dipropyl-dithiocarbamic acid-n-butyl ester-w-sodium sulfonate as a brightening agent, the steps which comprise adding to said electroplating baths from 0.01 to 20 gm./liter of 2-diethylamino-ethylchloride-1, and electrodepositing copper from said baths, whereby the impurities contained in said hard water and said technical grade copper salts are prevented from interfering with the brightening action of the brightening agent.

6. In a process of producing bright copper electrodeposits from acidic copper electroplating baths comprising hard water, technical grade copper salts and a sulfonic acid brightening agent, the steps which comprise adding to said acidic copper electroplating baths from 0.01 to 20 gin/liter of N-Z-chloroethyl-piperidine, and electrodepositing copper from saidbaths, whereby the impurities contained in said hard water and said technical grade copper salts are prevented from interfering with the brightening action of the sulfonic acid brightening agent.

7. The process according to claim 6, wherein said brightening agent is N,N-diethyl-dithiocarbamic acid-n propyl ester-w-sodium sulfonate.

8. In a process of producing bright copper electrodeposits from acidic copper electroplating baths comprising hard water, technical grade copper salts and a sulfonic acid brightening agent, the steps which comprise adding to said acidic copper electroplating baths from 0.01 to 20 gm./liter of the quaternary ammonium compound formed by reacting morpholine with epichlorohydrin, and electrodepositing copper from said baths, whereby the impurities contained in said hard water and said technical grade copper salts are prevented from interfering with the brightening action of the sulfonic acid brightening agent.

9. The process according to claim 8, wherein the brightening agent is N,N-diethyl-dithiocarbamic acid-npropyl ester-w-sodium sulfonate.

10. In a process of producing bright copper electrodeposits from acidic copper electroplating baths comprising hard water, technical grade copper salts and a sulfonic acid brightening agent, the steps which comprise adding to said acidic copper electroplating baths from 0.01 to 20 gm./liter of the quaternary ammonium compound formed by reacting diethylamine with epichlorohydrin, and electrodepositing copper from said baths, whereby the impurities contained in said hard water and said technical grade copper salts are prevented from interfering with the brightening action of the sulfonic acid brightening agent.

ll. The process according to claim 10, wherein the brightening agent is N,N-diethyl-dithiocarbamic acid-npropyl ester-w-sodium sulfonate.

(References on following page) 7 8 References Cited in the file of this patent OTHER REFERENCES UNITED STATES PATENTS Versenes," Bersworth Chem. Co., Framingham, Mass., 2,707,166 Brown et a1. Apr. 26, 1955 IL f 1952- Narcus: Metal Flnlshmg, vol. 50, pp. 5462, March FOREIGN PATENTS 5 1952 461,186 Canada Nov. 22, 1949 Sequestrene, Alrosen Chem. Co., Providence, R. 1.,

888,493 Germany Sept. 3, 1953 p. 2 Y 1952- 

3. IN A PROCESS OF PRODUCING BRIGHT COPPER ELECTRODEPOSITS FROM ACIDIC COPPER ELECTROPLATING BATHS COMPRISING HARD WATER, TECHNICAL GRADE COPPER SALTS AND A SULFONIC ACID BRIGHTENING AGENT, THE STEPS WHICH COMPRISE ADDING TO SAID ACIDIC COPPER ELECTROPLATING BATHS FROM 0.01 TO 20 GM./LITER OF A COMPOUND, FREE FROM CARBOXYL GROUPS HAVING THE STRUCTURAL FORMULA 